62 STUDY AND IDENTIFICATION OF BACTERIA 



hibits marked pleomorphism and Gram variations, and grows best on egg albumin 

 agar of plus 3 reaction as the cause of arthritis deformans and alveolar osteitis. 

 Inoculation of cultures of this organism into or around the knee-joints of rabbits 

 has produced lesions similar to those of rheumatoid arthritis. 



Of the nonpathogenic streptococci the most important one is S. lacticus, which 

 is described under milk. This differs from S. pyogenes in growing at lower tempera- 

 tures and having greater viability. It is a normal inhabitant of cows' dung. 



SARCINA FORMS 



These are best observed in hanging-drop preparations, when they 

 can be seen as little cubes, like a parcel tied with a string, and by noting 

 them when turning over, it will be seen that they are different from the 

 tetrads which only divide in two directions of space. At times the 

 packet formation is not perfect and it will be difficult to distinguish 

 such as sarcinae. All sarcinae stain by Gram. If the staining of sar- 

 cinae be too deep it may obscure the lines of cleavage. Sarcinae are non- 

 motile. 



i ^Various sarcinae have been isolated from the stomach, especially when there is 

 stagnation of stomach contents. Sarcinse have also been found in the intestines. 

 In plates the S. lutea is frequently a contaminating organism, being rather constantly 

 present in the air. The demonstration of sarcina morphology should always be 

 made from liquid media, as bouillon. Urine makes an excellent medium. 



MICROCOCCUS FORMS 



This grouping includes all cocci which do not show chain or packet 

 formation. It will be found convenient to divide them into two classes 

 according to their staining by Gram. The M. tetragenus, S. pyogenes 

 aureus and the Pneumococcus stain by Gram, while the Gonococcus, 

 the Meningococcus, the M . catarrhalis and the M . melitensis are Gram- 

 negative. 



M. Tetragenus. This organism is frequently found associated with 

 other organisms in sputum, especially with tubercle and influenza 

 bacilli. The colonies are white, slightly smaller than staphylococci and 

 are quite viscid. 



It was formerly considered unimportant in disease, but the idea now prevails that 

 it is responsible for many abscesses about the mouth, especially in connection with 

 the teeth. Injected subcutaneously into Japanese mice, it produces a septicaemia 

 and death in three or four days. The blood shows great numbers of encapsulated 

 tetrads. It has been reported twice as a cause of septicaemia in man. 



